what's the difference between using an ordinary pointer and a "pointer to member"?

[kevintse]

#include <iostream>
using namespace std;
#define PRINT(x) cout << #x " = " << x << endl;

class Object{
public:
	Object():i(5){}
	 int i;;
};

int main() {
	Object o;
	o.i = 5;
	int* p = &(o.i);
	PRINT(*p);

	int Object::* p2m = &Object::i;
	PRINT(o.*p2m);
	return 0;
}

the two PRINT macros produce this:

*p = 5
o.*p2m = 5

could you tell me what the difference is between using them? when should i choose one over another? and why?
Thank you in advance!

[Salem]

Well ordinarily, your data in the class wouldn't be public to begin with.

Making it public defeats the whole purpose of having classes at all.

[ArkM]

Read about:
- pointers to member functions:
http://www.gidforums.com/t-18332.html
- pointer to data members:
http://www.icce.rug.nl/documents/cplusplus/cplusplus15.html#l219